The present invention relates to an arrangement for the automatic engagement in case of impact accidents and emergency braking situations of a hazard warning system of a motor vehicle which is adapted to be selectively engaged and disengaged by hand, with an inertia switch that responds at least to impact-like accelerations acting in the road plane of the motor vehicle and then engages the hazard warning system by way of a circuit arrangement with a self-holding circuit while by-passing a manually actuatable hazard warning turn-on switch.
Circuit arrangements are already known in the prior art (DE-PS No. 27 06 962, DE-OS No. 39 37 040) which include an inertia switch whose response threshold is determined by the tilting inertia assisted by magnetic action of a conically truncated body against accelerations acting in the road plane of the vehicle. After overcoming this tilting inertia, an electric switch is closed with an inclined positioning of the body, which activates directly a circuit arrangement with a self-holding circuit which, in its turn, engages the hazard warning system of the vehicle.
As this arrangement is intended to automatically engage the hazard warning system, in addition to situations involving collisions with obstacles (other vehicles, guide rails, etc.), also in case of emergency braking situations, the tilting inertia of the body has to be selected relatively low in order that also not-impact-like-starting (brake) decelerations are able to deflect the body out of its rest position.
However, this leads to the fact that also a short, vehement actuation of the brakes or impacts as are exerted on the vehicle by road surface unevennesses such as pot holes and curbstone edges, when rolling over the same, may lead to the immediate but unintentional engagement of the hazard warning system so that the vehicle driver and surrounding traffic participants would be unnecessarily irritated.
The DE-OS No. 22 18 668 also discloses an arrangement of the aforementioned type which includes an inertia switch with an inertia mass returnable by spring force whose response threshold is adjustable by changing the spring prestress.